July 12, 2012

Clovis people had Western Stemmed Tradition company

A day after the paper by Reich et al. on the three waves of colonization of the Americas in Nature, there is another paper in Science which adds to the complexity of the period of the continent's early settlement.

While the genetics of modern populations can presently identify only one wave of 'First Americans' followed by two much less important waves associated with the later spread of Na-Dene and Eskimo-Aleut, we have known for some time that there were pre-Clovis people living in America. The new research suggests that at the time of the Clovis culture itself, or even prior to it, there was another distinctive archaeological culture.

Stone spearheads and human DNA found in Oregon caves, anthropologists say, have produced firmer evidence that these are the oldest directly dated remains of people in North America. They also show that at least two cultures with distinct technologies — not a single one, as had been supposed — shared the continent more than 13,000 years ago.

In other words, the Clovis people, long known for their graceful fluted projectile points, were not alone in the New World. The occupants of Paisley Caves, on the east side of the Cascade Range, near the town of Paisley, left narrow-stemmed spear points shaped by different flaking techniques. These hunting implements are classified as the Western Stemmed Tradition, previously thought to be younger than the Clovis technology.

"One of the central questions has been whether the technological evolution of hunting tools such as dart and spearheads can be attributed solely to the Clovis culture and the knowledge that these people brought from the Old World. During our excavations in the Paisley Caves we've found a completely different type of dart points. But these new points are of a completely different construction from those found in the Clovis culture. As our radiocarbon dating shows, the new finds are as old, or possibly older than the Clovis finds, which proves that the Clovis culture cannot have been the 'Mother technology' for all other technologies in America. Our results show that America was colonized by multiple cultures at the same time. And some perhaps even earlier than Clovis."

The genetic results are themselves quite interesting:

The 26 new specimens attributed to humans were radiocarbon dated byaccelerator mass spectrometry, and they range in age from 2295 ± 15 to 12,265 ± 2514Cyr., confirming the previously established range of occupation of these caves from beforeClovis in the late Pleistocene, to the late Holocene. Twenty-one specimens belonged to mitochondrial founder haplogroup A, screened for the presence of the A – G SNP atnucleotide position (np) 663 (all positions given with reference to the revised CambridgeReference Sequence). Five belonged to haplogroup B, characterized by a 9 base-pair (bp)deletion following np 8281, also present in eight of the coprolites assigned to haplogroupA (Table S17). The presence of this 9bp deletion after nucleotide 8281 has beenpreviously reported for haplogroup A (42-43), but it has also been reported forhaplogroups C and D. Therefore our results are not likely a product of crosscontamination both at the excavation site or in the lab.

Clovis Age Western Stemmed Projectile Points and Human Coprolites at the Paisley Caves

Dennis L. Jenkins

The Paisley Caves in Oregon record the oldest directly dated human remains (DNA) in the Western Hemisphere. More than 100 high-precision radiocarbon dates show that deposits containing artifacts and coprolites ranging in age from 12,450 to 2295 14C years ago are well stratified. Western Stemmed projectile points were recovered in deposits dated to 11,070 to 11,340 14C years ago, a time contemporaneous with or preceding the Clovis technology. There is no evidence of diagnostic Clovis technology at the site. These two distinct technologies were parallel developments, not the product of a unilinear technological evolution. “Blind testing” analysis of coprolites by an independent laboratory confirms the presence of human DNA in specimens of pre-Clovis age. The colonization of the Americas involved multiple technologically divergent, and possibly genetically divergent, founding groups.

5 comments:

"Five belonged to haplogroup B, characterized by a 9 base-pair (bp)deletion following np 8281, also present in eight of the coprolites assigned to haplogroupA (Table S17). The presence of this 9bp deletion after nucleotide 8281 has beenpreviously reported for haplogroup A (42-43), but it has also been reported forhaplogroups C and D."

I haven't read either of the papers but the presence of 9bp deletion on hg B, A and C may indicate its higher phylogenetic position and hence greater antiquity globally, as I suggested at http://anthropogenesis.kinshipstudies.org/2012/03/on-the-origin-of-mtdna-haplogroup-b-in-the-americas-9-bp-deletion-in-america-asia-and-africa/.

I think you can make an argument that B6 should be linked with B4'5 by 8281-8289d. That looks just likely, or more likely, than linking B6 and R11 by A12950G.

But apart from that case, 8281-8289d is a somewhat common mutation that occurs in many different subclades, typically fairly low down the tree, so it very clearly does not have a higher phylogenetic position linking A, B and C.

All or nearly all mtDNA haplogroup B sequences have the 9 base pair deletion. Only a few sequences in other haplogroups also have it. In haplogroup A, most (but not all) of these sequences belong to A2d1.

"But apart from that case, 8281-8289d is a somewhat common mutation that occurs in many different subclades, typically fairly low down the tree, so it very clearly does not have a higher phylogenetic position linking A, B and C."

It's precisely in such a relic mutation as 9bp deletion that you anchor a phylogenetic tree. You don't declare a mutation homoplastic simply because it's pervasive. 8281-8289d is found in America, Asia, Polynesia, Australia, Near East, Sub-Saharan Africa. It's already a pretty upstream mutation as it's found on L0a2 (Pygmies) in addition to T2f, I2b, I5a1, D4b1b2, B6, B5, A2d1, M1a1d, M6b, C, etc.

This pervasiveness suggests that we may need to re-consider the existing trees that cluster the sequences containing 9bp deletion into separate lineages. If deletion is the ancestral state at 8281-8289, then we'll have 9bp insertion on the vast majority of human mtDNAs. The residual traces of 9bp deletion are found everywhere, but at generally low frequencies. This is to be expected from an old mutation.

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